In recent years, learning commons have been increasingly introduced into university buildings as spaces that promote active learning among students. This study reports on the operational outcomes of energy conservation strategies implemented in the air-conditioning system of a university building designed with a large-scale atrium serving as a primary circulation space and accommodating a learning commons to encourage active use. The learning commons in the target building is planned with an underfloor air distribution (UFAD) system to condition the occupied zone, thereby mitigating thermal disturbances caused by its connection to the atrium. A similar UFAD system is also applied in a high-ceiling library space. Since UFAD systems generally operate with higher supply air temperatures, the chilled water supply temperature can also be set higher. In addition, lecture rooms are equipped with a ceiling radiant air-conditioning system, which similarly requires a higher chilled water temperature to prevent condensation. Based on these characteristics, the building adopts a central heat source system utilizing high-efficiency air-cooled modular chillers. Two separate chilled water distribution systems are designed: one supplying chilled water at approximately 7 °C to outdoor air-handling units, and the other supplying chilled water at approximately 10 °C to UFAD units and related equipment. Independent heat source units are installed for each system to enhance equipment performance by adjusting the chilled water temperature according to the specific requirements of each system. Performance measurements of the heat source units during operation showed that the 7 °C chilled water system achieved a coefficient of performance (COP) of approximately 5, which is close to the rated performance under Japanese Industrial Standards (JIS) conditions. In contrast, the 10 °C chilled water system exhibited a 10-20% improvement in performance compared with the rated value, confirming the energy-saving effect of adopting two chilled water systems. Furthermore, the water transportation factor (WTF), an indicator of efficient operation, remained above the threshold value of 35, demonstrating favorable performance in secondary chilled water pumping.
Shih et al. (Tue,) studied this question.